DESCRIPTION (provided by investigator): Site specific recombinases (SSRs) play a critical role in mammalian genetic analysis. The central goal of the work proposed in this application is to develop a new SSR, for genome engineering in stem cells and mice. At the present time, two SSRs, Cre and Flpe, are widely used and have been incorporated into the gene targeting and gene trapping designs of the International Knockout Mouse Consortium. Additional SSRs with target site specificities differing from Flpe and Cre will enable new strategies that are a significant advancement beyond current approaches. The central goal is to test the capabilities of the Dre recombinase as an additional SSR for use in ES cells and mice. Based on previously published work and new preliminary studies in my lab, we know that although Dre is related to the Cre recombinase, it does not react with the Cre target site loxP in bacteria or in mammalian cells. The work proposed in this application will carefully test the efficiency and specificity of the Dre recombinase in stem cells and in the developing central nervous system of mice. The proposed studies will provide essential new information required for the use of a new recombinase research tool by the research community. We will also generate valuable research resources including a mouse strain that expresses Dre in neural precursors as well as a Dre activity reporter mouse strain and embryonic stem cells. PUBLIC HEALTH RELEVANCE The proposed experiments will generate a new site-specific recombinase tool for use in genome engineering applications. This genetic tool will be useful to the research community for generating animal models of human genetic diseases and disorders.